Defogging and dehumidifying devices are known in which air of a foggy region, generally with a relative humidity of 100 percent is drawn into contact with a condenser and subsequently an reheater both of which are parts of a closed refrigeration system or refrigerant cycle. The air leaves the defogging device as an unsaturated and slightly heated air stream. The blow is disposed in the downstreamm portion of the defogging device.
It is known in the art to use the above-described defogging devices for the defogging of small regions. Humid air is passed through the device and moisture in the foggy air is condensed or even frozen to ice at a heat exchange in which the refrigerant is vaporized and therefore abstracts heat from the humid air. In the downstream heat exchanger, at which the refrigerant is condensed after compression, the dehumidifier air recovers heat from the refrigerant. The air stream which leaves the defogging device is thus unsaturated and slightly warmer than the ambient foggy air.
This heat gain is a disadvantage in the known air-dehumidifiers for closed rooms, and a heating of such rooms must be prevented by heat removal. However, with the above-described defogging device the heat gain may be somewhat advantageous since it allows ambient air of a high relative humidity to mix with the unsaturated air and maintain the region covered by the emerging air mixture free from fog.
The temperature of the inlet and the outlet of a defogging device adjusted when it is necessary to compensate for for varying temperature and humidity of the ambient air to be be defogged.
The above-described defogging devices are highly effective for limited areas, but do not fully meet the more stringent requirements for large regions, i.e. airstrips of airports and highway stretches. The reason for this is that the effectivity of each individual defogging device and the joint defogging device is detracted from the variations in climatic conditions, which seldom are constant.